This invention relates to vehicle door latches, and more particularly, to a vehicle door latch that has an anti-theft feature.
Automotive vehicles have a door latch on each vehicle door to latch the door in the closed position. Each vehicle door latch includes a lock that is commonly actuated from inside the vehicle by a readily accessible sill button or other manually operable device on the door. The vehicle door lock for the front doors is conventionally operated from outside the vehicle as well, usually by a key lock cylinder that has a removable key to deter theft.
Upscale automotive vehicles commonly employ a power lock system as a convenience feature. The power lock system commonly employs an electrically powered actuator associated with each door latch (and sometimes also with the trunk latch and fuel filler door latch) to move the door lock between its locked and unlocked positions. The actuators are controlled in a variety of ways. In a central vehicle door lock system, or at least in the American version of such a system, all the actuators are controlled by any one of three switches. These three switches are located in the key lock cylinder for the driver's door and on the interior trim panel for each front door. Thus, all doors can be locked or unlocked from outside the vehicle by means of the key lock cylinder switch in the driver's door, or from inside the vehicle by means of the switches next to the driver or the front seat passenger.
Manual and power door lock systems have a common problem. As indicated above, the front door locks are commonly actuated from outside the vehicle by a key lock cylinder that has a removable key to deter theft. In four door vehicles, the rear door locks cannot be unlocked from outside the vehicle. However, the door lock for any door is commonly actuated from inside the vehicle by a readily accessible sill button or other manually operable device that does not have any theft deterrent feature. Consequently, the theft deterrent aspect of the key operated door lock can be circumvented by breaking a vehicle window, reaching inside the vehicle and unlocking the vehicle door by means of one of the inside sill buttons or its equivalent.
To overcome this circumvention technique, an anti-theft feature has been developed for vehicle door latches as a counter measure in the case of electrically operated door latches used in central locking or power door lock systems. See, for instance, U.S. Pat. No. 4,342,209 granted to Frank Kleefeldt Aug. 3, 1982; U.S. Pat. No. 4,364,249 granted to Frank Kleefeldt Dec. 21, 1992; U.S. Pat. No. 4,440,006 granted to Frank Kleefeldt Aug. 3, 1984; and U.S. Pat. No. 4,727,301 granted to Fulks et al. Feb. 23, 1988.
By way of example, U.S. Pat. No. 4,342,209 granted to Frank Kessfeldt Aug. 3, 1982, discloses a central vehicle door lock system that has several door latches each of which includes a detent and a mechanism inside the door latch that moves the detent between a lock position securing the door closed and an unlock position that allows the door to be unlatched and opened. Each door latch is associated with a servoactuator that has an actuator that moves the detent via this internal mechanism; the actuator, in turn, being moved by an operator. The operator itself can be moved into an anti-theft position by a servomotor to engage a lock pawl so that the actuator is locked in a locked position. The servomotors are all controlled by a central key switch which can operate all the door latches between the lock, unlock and anti-theft position. None of the door latches can be unlocked when the anti-theft feature is engaged.
One disadvantage of prior art systems is that there is no practical way for an authorized person to enter the automobile if the anti-theft feature cannot be disengaged for one reason or another. This possibility can occur, for instance, in the case of an electrical power failure in a central locking system.